Class IntMean
- java.lang.Object
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- org.apache.commons.statistics.descriptive.IntMean
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- All Implemented Interfaces:
java.util.function.DoubleSupplier
,java.util.function.IntConsumer
,java.util.function.IntSupplier
,java.util.function.LongSupplier
,IntStatistic
,StatisticAccumulator<IntMean>
,StatisticResult
public final class IntMean extends java.lang.Object implements IntStatistic, StatisticAccumulator<IntMean>
Computes the arithmetic mean of the available values. Uses the following definition of the sample mean:\[ \frac{1}{n} \sum_{i=1}^n x_i \]
where \( n \) is the number of samples.
- The result is
NaN
if no values are added.
This class uses an exact integer sum to compute the mean. Supports up to 263 (exclusive) observations. This implementation does not check for overflow of the count.
This class is designed to work with (though does not require) streams.
This implementation is not thread safe. If multiple threads access an instance of this class concurrently, and at least one of the threads invokes the
accept
orcombine
method, it must be synchronized externally.However, it is safe to use
accept
andcombine
asaccumulator
andcombiner
functions ofCollector
on a parallel stream, because the parallel implementation ofStream.collect()
provides the necessary partitioning, isolation, and merging of results for safe and efficient parallel execution.- Since:
- 1.1
- See Also:
- Mean (Wikipedia)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
accept(int value)
Updates the state of the statistic to reflect the addition ofvalue
.IntMean
combine(IntMean other)
Combines the state of theother
statistic into this one.(package private) static double
computeMean(Int128 sum, long n)
Compute the mean.static IntMean
create()
Creates an instance.double
getAsDouble()
Gets the mean of all input values.static IntMean
of(int... values)
Returns an instance populated using the inputvalues
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface org.apache.commons.statistics.descriptive.StatisticResult
getAsBigInteger, getAsInt, getAsLong
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Field Detail
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SMALL_N
private static final long SMALL_N
Limit for small sample size where the sum can exactly map to a double. This is conservatively set using 2^21 values of 2^31 (2^21 ~ 2 million).- See Also:
- Constant Field Values
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sum
private final Int128 sum
Sum of the values.
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n
private long n
Count of values that have been added.
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Constructor Detail
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IntMean
private IntMean()
Create an instance.
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IntMean
private IntMean(Int128 sum, int n)
Create an instance.- Parameters:
sum
- Sum of the values.n
- Count of values that have been added.
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Method Detail
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create
public static IntMean create()
Creates an instance.The initial result is
NaN
.- Returns:
IntMean
instance.
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of
public static IntMean of(int... values)
Returns an instance populated using the inputvalues
.- Parameters:
values
- Values.- Returns:
IntMean
instance.
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accept
public void accept(int value)
Updates the state of the statistic to reflect the addition ofvalue
.- Specified by:
accept
in interfacejava.util.function.IntConsumer
- Parameters:
value
- Value.
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getAsDouble
public double getAsDouble()
Gets the mean of all input values.When no values have been added, the result is
NaN
.- Specified by:
getAsDouble
in interfacejava.util.function.DoubleSupplier
- Returns:
- mean of all values.
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computeMean
static double computeMean(Int128 sum, long n)
Compute the mean.This is a helper method used in higher order moments.
- Parameters:
sum
- Sum of the values.n
- Count of the values.- Returns:
- the mean
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combine
public IntMean combine(IntMean other)
Description copied from interface:StatisticAccumulator
Combines the state of theother
statistic into this one.- Specified by:
combine
in interfaceStatisticAccumulator<IntMean>
- Parameters:
other
- Another statistic to be combined.- Returns:
this
instance after combiningother
.
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